1. Field of the Invention
The present invention relates to an internal combustion engine.
2. Description of the Related Art
In an engine in which fuel is directly injected into the combustion chamber, if fuel injected by the fuel injector directly impinges upon the inner wall of the cylinder, lubricating oil for lubricating between the inner wall of the cylinder and the outer wall of the piston is diluted by the injected fuel, and thus a problem arises in that the inner wall of the cylinder is damaged, or in some cases, a heat seizure of the piston will occur.
In a known engine, a depression is formed on the top face of the piston, and a single fuel injector is arranged on the inner wall of the cylinder head. Fuel is injected twice from the fuel injector toward the depression, i.e., at the beginning of the intake stroke and at the end of the compression stroke (Japanese Unexamined Patent Publication No. 2-169834). If fuel is injected toward the depression, the fuel does not directly impinge upon the inner wall of the cylinder, and thus it is possible to prevent damage to the inner wall of the cylinder and a heat seizure of the piston.
Where fuel is injected twice, if the fuel is injected at the beginning of the intake stroke and at the end of the compression stroke, the positions of the piston when two fuel injections are carried out are almost the same. Accordingly, in this case, by using a single fuel injector, it is possible to inject fuel toward the depression.
Nevertheless, where the positions of the piston positioned when two fuel injections are carried out are considerably different, if the direction of injection is determined so that fuel is directed toward the depression at the time one of the fuel injections carried out when the position of the piston is high, at the time of the other fuel injection, which is carried out when the position of the piston is low, fuel is not directed toward the depression but toward the inner wall of the cylinder and the fuel directly impinges upon the inner wall of the cylinder. As a result, a problem arises in that the inner wall of the cylinder is damage, and in some cases, a heat seizure of the piston will occur.